Tandem mass spectrometry in the study of fatty acids, bile acids, and steroids

Abstract

Over the last 50 years, the mass spectrometry of lipids has evolved to become one of the most mature techniques in biomolecule analysis. Many volatile and non-polar lipids are directly amenable to analysis by gas-chromatography-mass spectrometry (GC-MS), a technique that combines the unsurpassed separation properties of gas-chromatography with the sensitivity and selectivity of electron ionization mass spectrometry. Less volatile and/or thermally labile lipids can be analyzed by GC-MS, following appropriate sample derivatization. However, many complex lipids are not readily analyzed by GC-MS, and it is these molecules that are the subject of the current review. Since the early 1970s, there have been three outstanding developments in mass spectrometry that are particularly appropriate in lipid analysis; i.e., the introduction of (i) fast atom bombardment (FAB); (ii) electrospray (ES); and (iii) tandem mass spectrometry (MS/MS). The FAB and ES ionization techniques will be discussed in relation to MS/MS, and examples of their application in biochemical studies will be presented. The review will concentrate on the analysis of fatty acids, bile acids, steroid conjugates, and neutral steroids.

Analysis of oxysterols by electrospray tandem mass spectrometry

“…There is general agreement as to the structure of the b 1 -12 and b 2 type ions, but some debate as to the structure of the b 2 -CH 2 type ions [53]. The use of deuterium labeled steroids in this current study provide further evidence for the b 1 -12 type ions to consist of the steroid A-ring plus C-19 but minus C-5; and the b 2 type ions to consist of the A ring, C-6 and C-19 (Scheme 3).…”

“…Traditionally, oxysterols are analyzed by GC-MS after derivatization of the hydroxyl groups to trimethylsilyl ethers [31,32]; alternatively cholesterol-like molecules can be analyzed by ES-MS and ES-MS/MS after one of a number of different derivatization reactions [53]. In the current study, molecules with a C 5 -3␤-ol structure have been oxidized to 3-oxo-⌬ 4 steroids and then derivatized to GP hydrazones.…”

Resolvin D1, protectin D1, and related docosahexaenoic acid-derived products: Analysis via electrospray/low energy tandem mass spectrometry based on spectra and fragmentation mechanisms

“…They also developed an analytical method and conducted stereochemistry studies of all the HDHAs produced by human platelets and rat brain homogenates using chiral LC-thermospray-MS and GC/MS (electron-impact ionization) [11]. Low-energy ionization primarily generates molecular (or pseudo-molecular) ions for collision-induced dissociation (CID) MS/MS analysis, through which the MS/MS spectra obtained are used widely to identify and elucidate the structures of lipid mediators derived from polyunsaturated fatty acids [12][13][14][15][16][17][18][19][20]. The lowenergy CID of eicosanoids includes charge-remote and charge-directed fragmentations [12,21], many of which occur through "␣-hydroxy-␤-ene like rearrangement" as referred to by Murphy, i.e., ␣-cleavage of the carbonOcarbon bond (␣ position to hydroxy group), facilitated by a double bond (ene) in the ␤ position [22].…”

A review of chromatographic methods for the assessment of phospholipids in biological samples

“…This is due to ESI ions being generated with lower internal energies. However, most published studies utilizing MS/MS for phospholipid analysis were done using FAB because this ionization technique was interfaced with mass spectrometers earlier (Griffiths, 2003). It has also been found that the fragments that are formed vary depending on the mass analyzer.…”

“…CID will also create characteristic fragment ions. PC will form ions at M-15, M-60 and M-86 owing to the fragmentation of the choline head group (Griffiths, 2003). PS has an M-87 ion in the negative mode, corresponding to serine loss.…”